/*

 * Licensed to the Apache Software Foundation (ASF) under one

 * or more contributor license agreements.  See the NOTICE file

 * distributed with this work for additional information

 * regarding copyright ownership.  The ASF licenses this file

 * to you under the Apache License, Version 2.0 (the

 * "License"); you may not use this file except in compliance

 * with the License.  You may obtain a copy of the License at

 *

 *     http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

package com.bff.gaia.unified.sdk.testing;



import com.bff.gaia.unified.sdk.coders.Coder;

import com.bff.gaia.unified.sdk.coders.CoderException;

import com.bff.gaia.unified.sdk.transforms.windowing.BoundedWindow;

import com.bff.gaia.unified.sdk.util.CoderUtils;

import com.bff.gaia.unified.vendor.guava.com.google.common.base.Supplier;

import com.bff.gaia.unified.vendor.guava.com.google.common.collect.ImmutableList;

import com.bff.gaia.unified.vendor.guava.com.google.common.collect.ImmutableSet;



import javax.annotation.Nullable;

import java.io.Serializable;

import java.util.Collection;



/**

 * A {@link Supplier} that returns a static set of {@link BoundedWindow BoundedWindows}. The

 * supplier is {@link Serializable}, and handles encoding and decoding the windows with a {@link

 * Coder} provided for the windows.

 */

final class WindowSupplier implements Supplier<Collection<BoundedWindow>>, Serializable {

  private final Coder<? extends BoundedWindow> coder;

  private final Collection<byte[]> encodedWindows;



  /** Access via {@link #get()}. */

  @Nullable

  private transient Collection<BoundedWindow> windows;



  public static <W extends BoundedWindow> WindowSupplier of(Coder<W> coder, Iterable<W> windows) {

    ImmutableSet.Builder<byte[]> windowsBuilder = ImmutableSet.builder();

    for (W window : windows) {

      try {

        windowsBuilder.add(CoderUtils.encodeToByteArray(coder, window));

      } catch (CoderException e) {

        throw new IllegalArgumentException(

            "Could not encode provided windows with the provided window coder", e);

      }

    }

    return new WindowSupplier(coder, windowsBuilder.build());

  }



  private WindowSupplier(Coder<? extends BoundedWindow> coder, Collection<byte[]> encodedWindows) {

    this.coder = coder;

    this.encodedWindows = encodedWindows;

  }



  @Override

  public Collection<BoundedWindow> get() {

    if (windows == null) {

      decodeWindows();

    }

    return windows;

  }



  private synchronized void decodeWindows() {

    if (windows == null) {

      ImmutableList.Builder<BoundedWindow> windowsBuilder = ImmutableList.builder();

      for (byte[] encoded : encodedWindows) {

        try {

          windowsBuilder.add(CoderUtils.decodeFromByteArray(coder, encoded));

        } catch (CoderException e) {

          throw new IllegalArgumentException(

              "Could not decode provided windows with the provided window coder", e);

        }

      }

      this.windows = windowsBuilder.build();

    }

  }

}